1. Field of the Invention
This invention relates to a zoom lens device and a method of assembling the same, and more particularly to a zoom lens device suitable for a video camera and the like and a method of assembling the same.
2. Description of the Related Art
In general, a zoom lens device is constituted by a focus lens group, movable lens groups and a master lens group.
In such a zoom lens device, for example, a zoom ring is rotated and the movable lens groups are moved back and forth in a direction of an optical axis under a predetermined relationship to thereby change the magnification, and a focus ring is rotated and the focus lens group is moved in a direction of an optical axis to thereby focus.
Now, as shown in FIG. 3, as for the movable lens groups, movable lens groups 1 and 2 are secured to lens frames 3 and 4, respectively. Then, the respective movable lens groups 1 and 2 are supported such that the respective optical axis of lenses thereof coincide with each other, with guide bars 8, 9 and 10 being mounted in guide holes 6 and 6 formed in the lens frames 3 and 4 and guide grooves 7 and 7 for bracing.
In order to arrange the lens frames 3 and 4 in a cam tube 11, the lens frames 3 and 4 are inserted into the cam tube 11 in a state where these lens frames 3 and 4 are supported by the guide bars 8, 9 and 10, and cam pins 12 and 13 formed on the lens frames 3 and 4 are coupled into cam grooves 14 and 15 which are formed in the cam tube 11. With this arrangement, by rotating the cam tube 11, the lens frames 3 and 4 are moved back and forth in the direction of the optical axis under a predetermined relationship.
However, in the conventional zoom lens device, the lens frames 3 and 4 should be inserted into the cam tube 11 in an unstable state in which the lens frames 3 and 4 are supported by the guide bars 8, 9 and 10, and further, in this unstable state, the cam pins 12 and 13 should be coupled into the cam grooves 14 and 15, so that such a disadvantage is presented that difficulties are felt in assembling.
Furthermore, the cam tube 11 is inserted into a lens barrel to be assembled in a manner to prevent the lens frames 3 and 4 from falling off, so that such a further disadvantage is presented that still more labor is required for assembling.